The Hallcrest Household Battery Tester is a thin flexible strip (packaged in a convenient vinyl storage pouch) that lights up to indicate battery strength and will last for years. Eliminates the guesswork associated with battery life. · Household Battery Tester · Just apply the ends of the strip to the battery and read! · Works with most common battery sizes including 1.5, AAA, AA, C, D 9v & PP3